(1) Field of the Invention
The present invention relates to a cleaning device for a fixing unit in an electrophotographic image forming apparatus, the fixing unit being formed of a heating member incorporating a heater and a pressing member that is put in press-contact with the heating member to fix an unfixed developer image formed on the surface of recording paper thereto by applying heat and pressure as the paper is passed through the nip between the heating member and pressing member, and more specifically, relates to a cleaning device for removing the developer remaining on the heating member and/or pressing member in the fixing unit.
(2) Description of the Prior Art
There are known electrophotographic image forming apparatuses, such as electrophotographic copiers, printers, etc., which comprise: a photoreceptor drum (image support) for supporting an unfixed developer image (toner image) that is obtained by developing an electrostatic latent image by a developer (toner); a transfer device for transferring the unfixed developer image on the photoreceptor drum to recording paper; and a fixing unit formed of a heat roller (heating member) heated by a heater such as a heat lamp etc., and a pressing roller (pressing member) abutted with a predetermined contact pressure against the heat roller.
The recording paper to which the unfixed developer image has been transferred by the transfer device is passed through the nip between the heat roller and the pressing roller of the fixing unit with its unfixed developer image surface facing the heat roller, so as to fix the unfixed developer image to the recording paper.
In addition to the image forming apparatuses for monochrome image forming such as black and white and the like, the electrophotographic image forming apparatuses also include color image forming apparatuses for printing color images with multiple colors of developers. In the case of such a color image forming apparatus, multiple colors of developer images are transferred to the recording paper (forming layers of developer images), so that the total thickness of the layers of unfixed developers is prone to be large.
When the total layer of the unfixed developers is thick as above, there may occur the problem with the conventional fixing unit that part of the developers adheres to the heat roller.
To deal with this problem, there has been a proposal of a cleaning device (Japanese Patent Application Laid-open Hei 9-160420) in which a cleaning member made of a felt or resin blade is put in press-contact with or abutted against the heat roller in order to remove the unnecessary developer adhering to the heat roller.
Use of the above cleaning device makes it possible with the cleaning member to collect the unnecessary developer from the heat roller when the fixing unit is in the initial condition, such as immediately after cleanup of the fixing unit, or the like.
However, after a period of a certain use of the image forming apparatus, the cleaning member of the cleaning device becomes dirty with the developer hence will degrade in cleaning performance. If this occurs, the unnecessary developer remains on the fixing rollers (heat roller and pressing roller), and part of the remaining developer may adhere to the recording paper hence spoil or dirty the front and rear sides of the recording paper.
In actual situations, adhesion of the remaining developer (toner) on the fixing rollers to the recording paper occurs such that adhesion of the developer corresponding to the print image information on the fixing rollers transfers to the recording paper when the recording paper passes through the nip between the heat roller and pressing roller (accordingly, the transferred remaining developer is not so conspicuous when it is seen in the printed recording paper).
In this case, the remaining developer on the fixing rollers collects and builds up at and around the contact points of multiple separation claws and a temperature detection sensor with the outer peripheral surfaces of the fixing rollers. When the remaining developer that has built up at these areas separates and drops due to some kind of impact and adheres to the recording paper, the developer is fused and fixed by heat from the heated fixing rollers, producing defects such as smudges or visible spots, etc., on the recording paper (the front and rear surfaces). Thus, the problem of image quality degradation occurs.